The present invention relates to a wireless communication apparatus, a wireless communication network and a software upgrading method and, in particular, to a wireless communication apparatus, a wireless communication network and a software upgrading method for upgrading software without the blackouts of communication services.
Wireless communication networks including wireless terminals and wireless communication apparatus have been introduced rapidly in addition to conventional wired communication networks. In the fields of wireless communication networks, Time Division Multiple Access (TDMA) communication networks for multiplying voice signals, for example, in a time division manner for communication have been adopted, and Code Division Multiple Access (CDMA) communication networks for code-multiplying voice signals, for example, with a spread code will be widely spread from now on. Thus, communications with any one can be performed any time and anywhere. These kinds of communication networks can operate by software included in each communication apparatus within a network and provide users of wireless terminals with various kinds of communication services such as voice communication and data communication. Therefore, the software for the communication apparatus must be upgraded properly every time the contents of each of communication services provided by the communication network advances.
A wireless communication apparatus is used for a wireless communication network and is called base station. The wireless communication is an interface apparatus for a wireless terminal and a communication network. The software as described above must be upgraded as required for providing various kinds of communication services. Therefore, various software upgrading methods have been proposed (such as JP-A-10-63498 and U.S. Pat. No. 2,980,201 or JP-A-10-320210). Upgrading the software for providing communication services is required in a general communication network. Therefore, software upgrading methods (such as JP-A-7-319683 and JP-A-2001-56756) have been proposed which allows the upgrading of software during the communication system (communication network) is in use without loss of reliability of the communication network (such as JP-A-7-319683 and JP-A-2001-56756).
Conventionally, a system for mutually connecting a wireless communication network and another communication network has been known for implementing diversity and hand-over for selectively synthesizing signals excellent in conversation quality based on the signal exchanged with plural base stations (such as JP-A-2001-16227). In a CDMA communication network, a soft hand-over technology (such as “3G TR25.832 V4.0.0”, issued by 3GPP, March 2001, Section 5.2.1) has been known for synthesizing signals from communications with plural base stations and selecting a communication path when a base station is changed in order to switch a communication path without blackouts.
In a general communication network, reliability is important in order to prevent a communication blackout. Therefore, a method for upgrading software set in inactive hardware has been adopted by providing hardware with redundancy as disclosed in JP-A-7-319683 and JP-A-2001-56756, for example. Thus, the software for providing communication services and for controlling operations of a communication network can be upgraded during the software is in use.
On the other hand, in a wireless communication network, communication with wireless terminals is performed within an area where radio waves from a base station can reach. The area is called cellular. A cellular of several km radius is generally used. In other words, the number of accommodatable users and covered area are much smaller than those of a conventional wired communication network (or a switched network). Therefore, in order to provide communication services widely, many base stations must be provided widely. Thus, the cost efficiency of the communication network is significantly lost by providing these many base stations with redundancy like the wired communication network facility as disclosed above. Furthermore, plural frequency bands and CDMA spread codes must be assigned. Thus, the limited resource is wasted, and the number of users is reduced, which also reduces the serviceability. Therefore, as disclosed in JP-A-10-63498 and U.S. Pat. No. 2,980,201 or JP-A-10-320210, for example, a method is generally known for selecting a base station in accordance with a proper rule and terminating a communication service in the base station for upgrading software. For example, an operator selects a base station having lower traffic in a time zone such as at midnight and upgrades software by protecting important calls and placing the base station off-line.
However, the method will impose larger loads on the operator for managing a wireless communication network in future, and the supply of economical wireless communication networks and communication services may be difficult. For example, a wireless communication network may be widely spread and the number of terminals used by users may increase. In this case, these terminals are used while moving, and the traffic of each base station always changes without blackouts. Furthermore, a communication network may be more used without recognizing time differences in a more global communication network, and the traffic may not be always reduced at midnight in Japan. Therefore, the selection of a base station having low traffic and the protection of important calls as described above may be difficult, and the loads on operators may increase. Furthermore, from users' point of view, the number of communication service blackouts (or communication disconnection) due to software upgrading may increase. Furthermore, the level of reliability and serviceability may decrease because the supply of new services delays due to the delay of the software upgrading. Therefore, a wireless communication apparatus, wireless communication network and method for operating them (software upgrading method) are desired for upgrading software of so-called on-line communication apparatus, which eliminates the blackouts of a communication service in use in a wireless communication network including wireless communication apparatus (base stations) without redundancy and which can provide the latest communication services.